Conventionally, a compound represented by a chemical formula Y3Al5O12 has been known widely under the name of yttrium aluminum garnet and used in solid-state lasers, translucent ceramics, etc.
Particularly, it is known that phosphors (YAG:Ce) obtained by adding Ce ions that function as luminescence centers to yttrium aluminum garnet are excited by electron beams, ultraviolet rays, corpuscular beams such as blue light, or electromagnetic irradiation, and emit visible light of yellow-green. It also is known that the 1/10 decay time of the phosphors is extremely short, which is a few ns or less. Therefore, the phosphors are used widely in various light-emitting devices (for example, see Patent Documents 1, 2 and Non-Patent Document 1).
Typical examples of light-emitting devices provided with such yttrium-aluminum-garnet-type phosphors include white LEDs in which blue LEDs and yellow phosphors are combined, projectors using LEDs or LDs and phosphors, illumination light sources using white LEDs, LCDs with LED backlight, and sensors and intensifiers using phosphors.
Further, in plasma display panels with a 3D image display function (3D-PDP), if the decay time of phosphors to be used is long, an overlap between a left eye image and a right eye image becomes worse due to moving image crosstalk, which causes a left eye image and a right eye image that are displayed by fast switching to overlap each other, whereby satisfactory 3D video images cannot be displayed. To cope with this, as green phosphors for PDP displaying 3D images, a technology using YAG:Ce with significantly short decay time has been proposed (for example, see Patent Document 3).